β Scribed by Y. Pomeranz
No coin nor oath required. For personal study only.
of roasted ground coffee by addttlon of inferior substitutes IS ascertamed by detcrrnmatlon of changes m composltlon or by specific quahtatlvc rcactlons, but the best means to detect adultcratlon IS furrushed by the mlcroscopc The m&hods mentioned fail m the case of admixture of cshausted, drlccl coffee residues. Natural varlatlons m characteristic constltucnts of ground roasted coffee amount to 2o"/" and more, and are partly Influenced by intcnslty of roasting and by the fmcncss to which the roasted coffee IS groundl. Any calculation based on thcsc data must allow for possible wide fluctuations and it 1s not safe to deduce adulteration by small amounts of exhausted coffee solely from dcvlations m "normal" composltlon I,lttle has been rccorded rcgardmg the USC of fluorescence analysis m cxamrnatlon of coffee purity. Chltory shows yellowish white fluorescence, whllc Tnraxaczl~ root 1s dctccted by its blue colour*. VALENTINE mvestlgatcd the appllcatlon of the chromatograplnc aclsorptlon method to the dlffercntlatlon of various kinds of coffee. Flltratcs of different starting materials, aftt5running through a column of alumina, gave chromatograms with very similar appearance, except that the violet fluorcscencc, m ultravlolct light, of malt mfuslons was weak as compared with that of genuine coffee The ultravlolct absorption of aqueous extracts of roasted coffee shows two broad absorption bands with maxima at cu. 285 rnp and cn. 320 rnp. Compounds such as caffeme and furfural have absorption maxmla 111 the 275-285 rnp range whllc chlorogemc acid IS reported to have a maximum at 323 rn@ Mcasuremcnt of the ultraviolet-absorbing components clctcrmmcd on diluted aqueous extract@ showed that a higher extraction of coloured substances -due to increased efficiency of extraction -was obtamcd with the more finely ground samples The concentrations of ultraviolet-absorbing components fell wrtll mcrcasmg severity of the roast Under normal brewing condltlons, the extracts of coffee beans from different sources show no slgmflcant differences m the levels of ultravlolet-absorbing components.
Genuine, ground roasted coffee examined under an ultravlolct lamp shows a bright colour, whereas exhausted, drlcd residues are dull. But the differences are too small to warrant differentiation and the colour may vary depending on the coffee berry variety and extent of roasting
The method described m this paper IS based on the fact that ground coffee dlstnbuted on filter paper shows on extraction with boiling water a brilliant ycllowlsh fluorescence spot surrounding the tested particle, whereas the exhausted particle shows no fluorescence.
π SIMILAR VOLUMES
Coffee beans of Coffea liberica (robusta) variety were roasted using convection and microwave heating. For roasting we used green coffee beans of 7.5% moisture content, and beans wetted to 10% moisture content and dried to 5% moisture content. The content of 5-hydroxytryptamides of carboxylic acids
Resonance-enhanced multi-photon ionization time-of-flight mass spectrometry (REMPIITOFMS) has been applied to the detection of volatiles in the headspace of brewed coffee and in the coffee roasting process-gas. A frequency quadrupled Nd : YAG laser (266 nm) was used for REMPI ionization (REMPI@266nm